The cheapest way to permanently sequester carbon involves ... fizzy water

In this episode, Ólafur Teitur Guðnason of Icelandic company Carbfix discusses his company’s approach to carbon sequestration by essentially making fizzy water and burying it deep underground.

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David Roberts

The idea behind the Icelandic company Carbfix is simple: pack water full of carbon dioxide (literally carbonate it, like a SodaStream) and inject it deep underground into Iceland’s porous basaltic rock. Minerals in the rock dissolve in the water, where they react with the CO2 to become calcium carbonates.

The carbon effectively becomes rock, which it will remain, for all intents and purposes, permanently. Or at least thousands and thousands of years. It is as long-term as carbon sequestration gets.

The idea dates back to 2006, but pilot injections didn’t begin until 2013 and it wasn’t until 2016 that a study published in Science confirmed that 95 percent of the CO2 in the water was mineralizing within two years — far faster than most had assumed possible.

Since it started, Carbfix has sequestered almost 100,000 metric tons of CO2 at its original site, but that is just a drop in the bucket compared to what it believes is possible. It has plans to make Iceland a major international carbon-burial hub and to replicate its technology in other geographies, maybe even in the shallow ocean.

When I visited the Carbfix operation in October and saw it in action, I was extremely intrigued and had a million more questions, so last week I got in touch with Ólafur Teitur Guðnason, Carbfix’s head of communications, to talk about where the company gets the CO2 it buries, where it plans to get it in the future, whether burial can work in other kinds of rocks and geographies, and exactly how much carbon Iceland can store.

All right, then, with no further ado, Ólafur Teitur Guðnason of Carbfix. Welcome to Volts. Thank you so much for coming.

Ólafur Teitur Guðnason

Thank you so much for having me.

David Roberts

So, Ólafur, I visited you guys when I was out in Iceland a few weeks ago and was very taken with this idea. And I don't know how I have been covering this stuff for so long without ever hearing about it, but it sounds like you guys are sort of on the verge of expanding. So I think probably a lot more people are going to be hearing about you soon. So to begin with, for listeners who are not familiar with your company, I'm going to run through the process and tell me if I get anything wrong. So you get a source of water, and we can discuss the source of water more later.

But you get water, you carbonate it more or less like a SodaStream carbonates water. You pump carbon dioxide into the water, and then you pump the water deep underground. And this carbonated water is heavier than normal water, so it tends to sink down to the bottom of the water table. And as it is sinking, the carbon dioxide in the water reacts with minerals in the rock to form calcium carbonates. Basically, the carbon dioxide in the water gets transformed into a form of rock, where it will then stay underground as rock for thousands of years. So you've permanently sequestered the carbon.

Is that more or less an accurate description?

Ólafur Teitur Guðnason

It's more than more or less accurate, I think. I'll give you a ten out of ten.

David Roberts

Excellent. Good. Well, I have so many questions about this, but the one thing I wanted to start with is the carbonation process of the water. Is that your intellectual property here? Is that your sort of main thing that you've pioneered here as a different way of carbonating water, or is there something special about the way you carbonate water?

Ólafur Teitur Guðnason

Yeah, that's one part of it. There are several elements to what we feel is proprietary or what we have solved — technology that we have developed. One thing is the capture of the CO2 emissions from the geothermal power plant, where we were kind of born as a research project within the company that runs the geothermal power plant, as well as universities both in Iceland and the US and France. So that is one element, yes. The dissolving of the CO2 with the water is another element, and the third element would be the way to inject it. So, yeah, there are different elements to this and at different stages of patenting.

David Roberts

Oh, I didn't realize that you were involved in the capture part of this. I knew that part of the CO2 that you're burying is coming from the geothermal plant, but I had kind of thought that was separate. Is this something that you're going to export if you try to export this model to other places or other countries? Is capture part of what you're promising, or are you mostly, do you think, going to be working with CO2 that someone else captured?

Ólafur Teitur Guðnason

Yes, mostly. Capturing is not our core field. It just comes from the fact that we were born out of this proximity to the geothermal power plant, so we needed a source of CO2, and we may, and have and are collaborating with other companies that run geothermal power plants, so our know-how is of use in that situation. But we are definitely not primarily a capturing company. There are other companies that focus on the capture part, and that has different technologies for different streams of CO2. So we're not too involved in that. We are mainly and primarily focused on getting it into the ground and mineralizing it and storing it.

David Roberts

So then when you carbonate the water, the physics of it, is it basically the same thing that's going on in a soda stream? Is there anything fancy going on, or is this just the carbonization that we're all familiar with?

Ólafur Teitur Guðnason

It's not too different, in essence. We have a stream of CO2, and then we shower it with water and pressurize so that it is completely dissolved. The difference is that we don't have the bubbles that you have in the soda stream or the soda drinks, mineral water that you drink, because these bubbles, they mean that the gas is escaping the fluid, so we don't want it to escape. So we are putting more of it into the water and making sure it's completely dissolved so that it doesn't rise back to the surface. And pressure takes care of that as well, as it continues to ensure this trapping mechanism underground as well when the solution gets into the ground.

So solubility trapping, as it's called, is kind of the first stage of trapping and isolating the CO2 from the surroundings or from the atmosphere. It's a pretty secure way of trapping CO2. But then, fairly soon, mineralization comes into play, as well as the second stage, and even more secure.

David Roberts

You know, when people think about what is basically a geological process of a gas being transformed into a stable mineral. I think of geological time frames. But your mineralization process, by which the CO2 is pulled out of the water and becomes rock, happens in two years, you say. Two years of the water being under